Resistor terminal construction



April 28, 1953 R wAKEFlELD 2,636,963

RESISTOR TERMINAL CONSTRUCTION Filed Au 16, 1950 FIG. 1

INVENTOR. Elam/a0 5. WAKEFIELD ATTORNEY Patented Apr. 28, 1953 RESISTORTERMINAL CONSTRUCTION Richard :E. B. Wakefield, Aldan, Pa., assign'orIto JShallcross Manufacturing Company, Cullingdale, :Pa.

Application .Augustlfi, 1950,1'Serlal No.f179,6.6.0

(Cl. EDI-A63) 1'2 LClaims. 1

iTliisinventi-un relates to 'a method-of termination for electricalresistors, and is the terminal construction therefor. The invention isparticularly adapted for use with wire wound resistors,' and is hereillustrated in connection with resistors of the power type impregnatedwith an insulating coating and-baked to "form aprotective shell over the.unit. It svill be understood, however, that my invention is not limitedto use with such resistors, but may be advantageouslyused 1 sin"otheritypes of resistors aswell.

In the past, :a variety iof difiiculties have been encountered with theterminals of such resist- .ors. Breakage of the wirewhere itis connectedto the terminal strip occurs, believed to be due to expansion of theterminal strip occurring during the baking, or to differences in thecoefficients of expansion of the parts, or to mechanical stressing ofthe terminal strip when connected into a circuit, and especially wherethe terminals also constitute the support for the resistor when in use.

Among the objects of this invention are to provide an improved terminalwhich is free from the diiiiculties mentioned, which is easily andquickly applied in the process of manufacturing the resistor, whichlends itself well to mass production of the resistors, which willprotect the fine as well as the heavier resistance wires against damageand possible breakage during manufacture and during service, and whichdoes not require matching of the coefficients of expansion of the core,coating, wire and terminals.

It is another object of this invention to provide an improved method ofeffecting termination of electrical resistors.

Still other objects and advantages of my invention will be apparent fromthis specification.

The features of novelty which I believe to be characteristic of myinvention are set forth with particularity in the appended claims. Myinvention, itself, however, both as to its fundamental principles and asto its particular embodiments, will best be understood by reference tothe specification and accompanying drawings, in which:

Figure 1 is a plan view of my improved terminal strip before applicationto a resistor;

Fig. 2 is an edge view thereof;

Fig. 3 is a perspective view of an end portion of a resistor showing astep in the process of applying my improved terminal thereto;

Fig. 4 is a similar view showing the terminal assembly completed, beforethe coating is applied to the resistor; and v Fig. 5 is a view of acomplete, coated resistor having the terminals applied thereto.

minal "in place.

2 Referring "now more particularly to Figs. 1 and 2,1;he terminal 'ispreferably formed of :a

pair of metal strips lfland H, of unequal length.

The strips are assembled to be co-extensive from one end and maybe spotwelded together along the line 12, as indicated in Fig. 1. Any suitablemetal may be used for the strips, and I have obtained very satisfactoryresults with #42 nickel steel for both strips.

After spot welding the strips together, or before if desired, theassembly is providedwithanchoring means,'such as a plurality 'of holes13 to permit the coating of the resistor unit to look through theterminal band to 'keep the "ter- The number, size and location of theholes are chosen as desired for the particular unit.

To apply the terminal, the longer strip in is bent around the resistorcore 1'6, usually tubular, so as to clamp the same, and the outwardlyextending end portions 14 and I5 are brought together and spot welded toeach other. This operation leaves the strip ll extending more or lesstangentially to the band. The end of the resistance wire I! wound oncore 16, is stripped of its insulation, if any, and is wrapped severaltimes around the strip H as shown in Fig. 3. The wrapping is desirablymade near the point of attachment of strip 1 I to strip I 0 and the wireis spot welded to the strip II. This establishes good electrical andmechanical connection between wire I! and strip H.

The strip l l is next bent around the core so as to lie on top of stripit whereupon the strips 10 and I l are secured together, as by spotwelding at the outer ends thereof. After completion of this step theterminal has the appearance shown in Fig. 4. This welding of the stripII at its ends, the welding of the wrapping of the wire around the stripand the clamping of the turns of the wrapping between the strips [0 andII effectively protects the resistance wire, normally the weakest partof the assembly, against strain and breakage.

The resistor unit may then be given a coating of ceramic material, whichcovers the resistance wire and the terminals except for the outwardlyextending portions in Fig. 4, and as shown in Fig. 5. After the ceramiccoating is dried and baked, the wire and the connections thereof to theterminals are firmly protected.

A coating which I have found particularly satisfactory for applicationby dipping is described and claimed in my patent application entitledResistor, filed concurrently herewith, but any other suitable coatingmay be used, or the resistor may be left uncoated. In the processdescribed in that case, the core 16 is of combustible material and isburned out after the first few coatings of ceramic material. Thereuponthe resistor is given one or more final coatings of ceramic material andthe ceramic material taking the place of core is unites with thepreviously applied coatings, and this applies also to the ceramicmaterial which penetrates the holes I3 to enhance the anchoring efiectthereof.

While I prefer to use spot welding for securin the strips together,especially in the case of power resistors, which run hot, the stripsmight be soldered or otherwise secured under appropriate circumstances.

In the specification, I have explained the principles of my inventionand the best mode in which I have contemplated applying thoseprinciples, so as to distinguish my invention from other inventions;and-I have particularly pointed out and distinctly claimed the part,improvement or combination which I claim as my invention or understoodthat modifications and changes may 'be made without departing from thespirit and scope thereof, as will be clear to those skilled in the art.

I claim: a 1. In a resistor, a core, a resistance wire on said core, anda pair of terminals for said wire,

.each comprising a first metallic strip the length of whichsubstantially exceeds the circumference of said core, said strip shapedto said core and having the ends thereof extending outwardly and weldedtogether, and a second metallic strip the length of which issubstantially less than that of the first strip, havin one end welded tosaid first strip near the mid point thereof and its other end welded tothe extending ends of the first strip, and said wire'encircling saidsecond strip at an intermediate point and welded thereto adjacent saidmid point connection.

2. The method of providing a terminal on a wire wound resistor whichcomprises securing one end of a shorter metal strip at a pointsubstantially midway of a metal strip of a length greater than thecircumference of the resistor, placing said longer stripcircumferentially around the resistor with its ends juxtaposed andextending outwardly, securing said ends together, wrapping the endportion of the resistor wire about said shorter strip and securing thewire to said strip, forming the free end of said strip against thelonger strip, and securing the longer and shorter strips together.

RICHARD E. B. WAKEFIELD;

' References Cited in the file of this patent UNITED STATES PATENTSNetherlands Nov. 15, 1946

